In a coupling reaction of introducing an oxymethyl group such as an alkoxymethyl group or a hydroxymethyl group into an aromatic ring using a palladium catalyst, it is reported to use an organotin reagent such as an alkoxymethyltin reagent and the like. As the organotin reagent used in the reaction, a methoxymethyl tributyltin reagent disclosed in Non-Patent Document 1, a hydroxymethyl tributyltin reagent disclosed in Non-Patent Document 2 or the like has been reported.    Non-Patent Document 1: Chem. Lett. 1984, 1225.    Non-Patent Document 2: Chem. Lett. 1985, 997.